feat: add container-use package and fix goose-cli libclang dependency

- Add dagger/container-use (v0.4.2) for containerized coding agent environments
- Fix goose-cli build by adding llvmPackages.libclang for bindgen
- Clean up skillsmcp package (remove custom fastmcp override, use nixos-unstable)
- Remove broken update.py script from goose-cli
- Add treefmt.toml for consistent formatting
- Update README with all current packages

packages/container-use/default.nix

@@ -0,0 +1 @@
+{ pkgs, ... }: pkgs.callPackage ./package.nix { }

packages/container-use/package.nix

@@ -0,0 +1,38 @@
+{
+  lib,
+  buildGoModule,
+  fetchFromGitHub,
+}:
+
+buildGoModule rec {
+  pname = "container-use";
+  version = "0.4.2";
+
+  src = fetchFromGitHub {
+    owner = "dagger";
+    repo = "container-use";
+    rev = "v${version}";
+    hash = "sha256-YKgS142a9SL1ZEjS+VArxwUzQX961zwlGuHW43AMxQA=";
+  };
+
+  vendorHash = "sha256-M7YhEm9Gmjv2gxB2r7AS5JLLThEkvtJfLBrB+cvsN5c=";
+
+  env.CGO_ENABLED = 0;
+
+  subPackages = [ "cmd/container-use" ];
+
+  doCheck = false;
+
+  ldflags = [
+    "-s -w -X main.version=v${version}"
+  ];
+
+  meta = with lib; {
+    description = "Containerized environments for coding agents";
+    homepage = "https://github.com/dagger/container-use";
+    changelog = "https://github.com/dagger/container-use/releases/tag/v${version}";
+    license = licenses.asl20;
+    mainProgram = "container-use";
+    platforms = platforms.linux ++ platforms.darwin;
+  };
+}